The Fossil Platyrrhines

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The Fossil Platyrrhines
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Modern Platyrrhines

• Traditional Classification
• Cebidae
• Atelinae (spider, wooly, howler, wolly spider)
• Pithecinae (saki, bearded saki, uacari)
• Aotinae (owl monkey)
• Callicebinae (titi)
• Cebinae (capuchin squirrel)
• Callitrichidae
• Marmosets, tamarins lion tamarins

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Platyrrhine Ecology

• All arboreal forms living in forests
• Small to medium size
• All diurnal except Aotus
• Retain P2 (DF 2-1-3-3)
• Callitrichids have lost M3 (DF 2-1-3-2)
• Tympanic ring fused to side of bulla

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Pleistocene and Holocene of the Caribbean

• Cave deposits on several islands have
  surprisingly yielded several taxa
• Xenothrix from Jamaica
• Paralouatta from Cuba
• Antillothrix from Hispaniola
• Implications of these recent finds
• Much greater diversity than expected
• Recent extinctions due to human influence?
• Single or multiple dispersals from mainland to
  Caribbean?

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Pleistocene of Brazil

• Cave deposits have yielded several taxa
• Protopithecus, first found in 1830s with recent
  skeleton found in 1990s
• Caipora, from same deposits in NE Brazil
• Both are very large and resemble atelines
• Several extant NWM taxa also found in these caves
• Callithrix, Cebus and Alouatta

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Late Miocene of La Venta

• In Colombian tropics, 13-12 mya
• Laventan SALMA
• Ca. 10 platyrrhine taxa with clear affinities to
  modern families or subfamilies
• Warm, tropical forested habitat
• Combination of archaic and modern mammals

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Some NWMs from La Venta

• Lagonimico conclutatus
• A giant tamarin?
• Owl monkey sized (ca. 1 kg)
• Very reduced upper M3
• No hypocones on upper molars
• Stirtonia
• Largest monkey at La Venta
• Resembles Alouatta (howler)

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The Miocene of Patagonia

• Southern Argentina and Chile
• Two biostratigraphic intervals identified
• Colhuehuapian SALMA is early Miocene (ca. 20
  mya), mainly from Chubut province, Argentina
• Dolichocebus, Tremacebus, Chilecebus, etc.
• Santacrucian is middle Miocene, from Santa Cruz
  Province, Argentina (ca. 17 mya)
• Soriacebus, Carlocebus, Homunculus
• Affinities with extant taxa are highly contested

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The Earliest Platyrrhines

• From the late Oligocene of Bolivia
• Salla is the locality, Deseadan SALMA
• Branisella and Szalatavus are the genera
• Both have 2-1-3-3 DF and retain hypocones on
  upper molars
• Both probably primitive Platyrrhines without
  clear connections to any single extant family or
  subfamily

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Origin of Platyrrhines

• A still unsolved puzzle with no easy answer
  because S America was an island continent
  thruout the Cenozoic
• Rafting across an oceanic barrier is the only
  (barely) plausible mechanism
• Two major possible source areas
• North America
• Africa

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North American Origin

• Cons
• No anthropoids known from N America
• Caribbean geology and plate tectonics is largely
  unknown
• Currents would not have been favorable
• Requires diphyletic origin of anthropoids
• Pros
• Shorter separating distance

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African Origin

• Pros
• Fayum anthropoids in L Eocene - E Oligocene
• Possible island hopping scenario with lowered sea
  level
• Currents would have been favorable for E-W
  dispersal
• Allows monophyletic origin of anthropoids
• Ancestor of S American rodents also present at
  Fayum
• Cons
• Long ocean barrier
• Primates are not considered to be well-adapted
  for long oceanic rafting trips, so this was a
  low-probability event but it obviously must have
  occurred!